1. Field of the Invention
This invention relates to providing a dual field of view sighting system.
2. Description of the Related Art
Conventional sighting systems used on a rifle or other visual targeting apparatus have advanced optical sights that enable precise aiming despite movement of the observer's eye.
For close quarter targeting, the preferred sight is the holographic or reflex “red dot” sight. This red dot sight projects an illuminated reticle that is visible to the observer with both eyes open. Because this sight is used for close quarter targeting, it produces no magnification and thus displays no telescope artifacts, while providing an unobstructed field-of view, unlimited eye relief, a large exit pupil, and no parallax.
For precision aiming at distant targets, the preferred sight is the 3-5× magnification telescope, which provides a minimum 5 mm exit pupil, an illuminated aiming reticle, and fine azimuth and elevation adjustments.
Red dot and telescope sights are typically sold separately as off-the-shelf components for mounting onto a rifle. Variable zoom telescopes available for precision aiming at distant targets usually provide 1× to 4× zoom capabilities.
One disadvantage of using a telescope alone is it does not provide for zero zoom (0×). Absence of magnification elements in the optical path distinguishes 0× from 1×. This prohibits its use for close quarter battles, where a wide field of view and no magnification is desired. Another disadvantage of the telescope is it requires that the user let go of the rifle for changing zoom modes, thus delaying acquisition of a target. Another disadvantage is the inability to view a Back Up Iron Sight (“BUIS”), which provides manual targeting through the sight. Additionally, fixed exit pupil sizes are too small for close quarter targeting.
To overcome these inherent telescope limitations, some manufacturers mount a rotating 3× telescope in front of the red dot sight. This arrangement allows the user to physically rotate the telescope in and out of the field of view for switching between close quarter targeting and precision distance aiming modes. For close quarter targeting, the telescope is rotated to the “down” position, so it is outside the field of view. This gives the user 0× zoom since the telescope is not positioned to magnify the incoming light. For precision aiming, the telescope is rotated to the “up” position, allowing it to intercept and magnify the light before it reaches the user's eye, thereby providing 4× zooming.
There are several disadvantages to this arrangement. First, changing modes still requires the user to let go of the rifle. Secondly, the rotating mechanism is a large, heavy external moving part. This not only adds size, weight and inconvenience, it also adds to the cost and complexity of the system.